Chromosomal studies of species of Rubiaceae (A. L. de Jussieu) from the Brazilian cerrado

The chromosomes of 14 species belonging to two subfamilies of the family Rubiaceae collected in the Brazilian cerrado were studied. In the subfamily Ixoroideae, five species (Alibertia concolor, A. edulis, A. sessilis, Genipa americana and Tocoyena formosa) had a chromosome number of 2n = 22 and one (Amaioua intermedia) showed polyploidy, with 2n = 66. All of the chromosome numbers were multiples of the more common basic number for this family (x = 11). In the subfamily Rubioideae, variations in the number of chromosomes were observed among tribes and genera, with 2n = 20 in the tribe Coccocypseleae (Coccocypselum lanceolatum), 2n = 28 in Spermacoceae (Borreria latifolia, B. verticillata and Richardia brasiliensis) and n = 11 in Coussareeae (Coussarea hydrangeifolia). In the tribe Psychotrieae, the variations included n = 11 (Palicourea rigida), 2n = 22 (Psychotria hoffmannseggiana) and 2n = 32 (Psychotria deflexa). The ideograms elaborated for 12 species were symmetrical (TF% varied from 47.45 to 38.01). The size of the chromosomes ranged from 1.26 to 7.33 μm and most were metacentric. The results show that chromosome size and morphology were insufficient to differentiate among groups within the Rubiaceae.